I feel like everybody is working against me, even people who I know care about me. Sometimes I feel like it's a big collaboration; a cruel experiment. I know that this isn't logical, but it doesn't stop me from noticing strange "coincidents". Sometimes I even feel like when I'm telling my best friend things about my day, he already knows. I'll notice what seems like people "tripping up" on what will suddenly feel like a scripted conversation or response. I've been feeling this way, on and off, for many years.
It doesn't make sense that all the people I know would collaborate to pick on me. I know that I am not that special. I know I shouldn't feel this way. But I do.
More than wanting to know 'why' I'm paranoid all the time, I want to know how to 'not' feel paranoid all the time.

I think what you're experiencing is just a natural thought-pattern. It's just that you're experiencing it a little more than other people.

What you can and should do is practice calming down. I'm talking about really calming down, and not entertaining the paranoid thoughts. If you see them and know they're BS, then start ignoring them and bringing yourself back to a calm space. Practice it over and over and you'll see that the paranoid thoughts will lose power, momentum, and then will reduce in frequency too.

2 other things you might want to explore: 1) martial arts classes and weightlifting. 2) check your posture and breathing. Whenever you notice it, make sure you're standing up straight and that your breathing is calm and steady. It'll help you tremendously. Don't overlook it.

I actually WOULDN'T go on an "fishing expedition" into your past to look for a trigger. It's good for some things, but imho, not for this.

The problem you have described is typical of people suffering from obsessive thought-forms, a kind of a persistent thought-pattern which persists for as long as the victim chooses to believe and pay attention to it.

Edahn is right in saying that it is a natural thought-pattern. We all have illogical thoughts every now and then constantly bombarding us, but seldom do we pay so much attention to any one of these illogical thoughts that happen daily. The moment too much attention is paid to any single one of these illogical thoughts, then it might grow to become a kind of a reoccurring thought-pattern, and a mental habit of sorts.

The tricky part about such mental annoyances is that the more a person resists or "tries" very hard not to think about it, as long as deep down there is still some percentage of an emotional and thus illogical belief in it, be it partly or fully, then the more the problem will actually grow. But for your encouragement, the reverse is also true.

These obsessive thought-forms basically survives upon 2 elements:

1) The victim's constant attention and belief in it. Even if he/she resists it, attention is still being paid to it.

2) The making use of the victim's innate fear/easily excitable nature/hidden sense of self-importance (just an example) etc etc in order to prevent him/her from seeing a clearer picture. Being an essentially illogical thing, it basically can appeal only to the irrational feelings or fears of the victim, but never to the clear mental reasoning of the victim. Therefore in almost every case the person will emotionally "feel" strongly that it is true, but never for once "reason" clearly that it is true.

Then once the person is made to fully or partially believe in these obsessive thought-forms, in due course this person will be subjected to little inconveniences of an everyday nature, such as when you describe that:

"I know that this isn't logical, but it doesn't stop me from noticing strange "coincidents". Sometimes I even feel like when I'm telling my best friend things about my day, he already knows. I'll notice what seems like people "tripping up" on what will suddenly feel like a scripted conversation or response."

This occurs simply because you are now looking at the world through your newly created, obsessive beliefs, rather than through a clear, reasonable mind. Beliefs are like various kinds of spectacles we wear to see the world with: If you wear a red spectacles for example, of course the world will be seen in a complete red etc.

The solution is a simple matter of creating a new thinking habit in your mind. Here are a few examples:

1) A healthy skepticism of any feelings that tries to make you "feel" that something is true, no matter how irrational it may be.

2) An increasingly lack of attention being paid to your obsessive thought-forms, be it from a new-found disbelieve in it, or from sheer laziness and lack of interest to pay it anymore time and attention (lol).

3) By constantly thinking the opposite direction every time you start to think that everybody is working against you etc. For example, whenever you start to think: "Oh me God! Person A knows exactly what I am going to tell him/her...!" etc etc, then think of the opposite possibilities such as "but it is also possible that it is nothing but yet another irrational obsessive thought-pattern, trying to emotionally blackmail me into believing in it..." etc etc.

Now that you know these, you can of course think of your own examples on how to solve your obsessive thought-patterns. So good luck, and best wishes in whatever you do in life!

Try not to feel too ashamed. If you can make a good argument for why your friends might be conspiring to evoke some response out of you without telling you about it, then maybe you're not crazy. If you can't think of any rational argument, then your concern is well-placed.